Andy Murray was made to work for a three-set win over Denmark's Kristian Pless in the third round of the San Jose Open on Wednesday.
Defending champion Murray saved break points in game six of the deciding set before winning 6-0 6-7 (5-7) 6-4.
"I felt a little sluggish but I wasn't playing badly," said Murray. "I was able to get through and on this court I was able to keep the ball down.
"I started to come to the net a bit - I had to try some different things."
Murray will face either Simon Greul or Hyung-Taik Lee in the last eight.
After racing through the first set and trading breaks early in the second, Murray lost concentration in the tie-break to allow Pless to level.
"Considering I had only played about 55 minutes of tennis in the last three weeks, it was good to get the win"
And the 19-year-old Scot then recovered from 15-40 at 2-3 in the final set before breaking in the next game and serving out the match.
"I got a bit frustrated at the start of the second set because he was basically tanking it at the end of the first, and then I was a bit cold as I hadn't hit the ball for a while," said Murray.
"I didn't play my best today but to give him credit, he played a really good second set - he started coming into the net and going for everything.
"These courts are so fast that it's difficult to come back when you are behind in sets.
"But considering I had only played about 55 minutes of tennis in the last three weeks, it was good to get the win."
Top seed Andy Roddick - a possible semi-final opponent for Murray - saw off Canadian Frank Dancevic 7-5 6-1 after losing the first 17 points of the match on Dancevic's serve.
"I was pretty uncomfortable those first couple of games," said Roddick, who will meet Sam Querrey in the third round.
"It got better as the match went on.
"I'm thankful I got that break in the first set because in a tie-breaker anything can happen. Then all of a sudden it could have been interesting."
Second seed James Blake thrashed Russia's Igor Kunitsyn 6-3 6-2 in his opening match and will take on Ivo Karlovic next.